1. Technical Field
The present invention relates to a nondestructive inspection method, more specifically to a nondestructive inspection method of testing insulators by using the frequency resonance functions of an insulator being inspected.
2. Description of the Related Art
To inspect anomalies of an insulator, a number of methods including a buzz method, a potential measurement method, a resistance measurement method and a field measurement method have been developed. Among these, a field-type detector for detecting a defective insulator that employs the field measurement method is commonly used. Nevertheless, since these methods inspect the anomalies by measuring the electrical properties such as split-voltage, insulation resistance and electric field of the insulator, they are unable to detect a crack of the insulator that is caused by repetitive mechanical and thermal stresses or a damage that is caused by a physical external force.